1. Field of the Invention
The present invention relates to a liquid crystal polyester resin composition, and a molded article obtained by using the same. More specifically, the present invention relates to a liquid crystal polyester resin composition having excellent thin-wall flowability and capable of producing a molded article having low warpage property while maintaining excellent heat resistance, and a molded article obtained by using the same.
2. Description of the Related Arts
Liquid crystal polyesters do not cause entangling even under melted condition since the molecule is rigid, form a polydomain having liquid crystal state and show a phenomenon of remarkable orientation of molecular chains along the resin flow direction due to shearing in molding, and generally called a melt liquid crystal type (thermotropic liquid crystal) polymer. Liquid crystal polyesters, due to this specific phenomenon, have excellent melt flowability, show high deflection temperature under load and continuous service temperature depending on the molecular structure, and do not cause deformation and blistering even if immersed in a melted solder of 260xc2x0 C. or higher.
Therefore, a resin composition obtained by filling reinforcing materials in the form of fiber typified by glass fiber and inorganic fillers typified by talc in a liquid crystal polyester is a material suitable for electric and electronic parts having a thin-wall or complicated portions.
However, recently, there is a development in products having smaller size and smaller thickness, and in lectric and electronic parts, particularly in connector parts, there is a demand for parts further having low warpage property while maintaining heat resistance, mechanical properties and flowability.
For example, JP No. 3045065 discloses a liquid crystal polyester resin composition obtained by filling glass fiber having a number-average fiber length of 0.12 to 0.25 mm in a liquid crystal polyester resin. However, due to use of glass fiber having a larger number-average fiber length, there is a problem of poor flowability and increase a warpage amount when a molded article having a thin part of 0.2 mm or less is produced.
JP-A No. 2000-178443 discloses a liquid crystal polymer composition obtained by compounding a filler in the form of fiber and a filler in the form of particle in a liquid crystal polymer. However, due to high melt viscosity of the liquid crystal polymer composition, there is a problem of increasing the warpage due to remaining stress in molding, leading to insufficient warpage reduction effect.
Further, JP-A No. 10-219085 discloses a liquid crystal polyester resin composition obtained by compounding inorganic fillers in the form of fiber and plate in a liquid crystal polyester at acompounding ratio (fiber/plate) of 1.7. However, there is still required an improvement in flowability and the warpage amount when molded article is formed.
Therefore, there has been a desire for development of a resin composition having excellent flowability and capable of producing a molded article having low warpage property while maintaining excellent heat resistance.
An object of the present invention is to provide a liquid crystal polyester resin composition having excellent thin-wall flowability and capable of producing a molded article having low warpage property while maintaining excellent heat resistance.
The present inventors have intensively studied to find a liquid crystal polyester resin composition having no problems as described above, and resultantly found that a liquid crystal polyester resin composition obtained by compounding specific inorganic fillers in the form of fiber and plate in a liquid crystal polyester resin having specific flow temperature, at a specific weight ratio, has excellent thin-wall flowability and is capable of producing a molded article having low warpage property while maintaining excellent heat resistance, leading to completion of the invention.
Namely, the present invention provides a liquid crystal polyester resin composition having an apparent melt viscosity of 10 to 100 Pa sec at a shearing rate of 1000 secxe2x88x921 and at a flow temperature 40xc2x0 C., obtained by compounding 10 to 100 parts by weight of an inorganic filler in the form of fiber and 10 to 100 parts by weight of an inorganic filler in the form of plate based on 100 parts by weight of a liquid crystal polyester resin, wherein the liquid crystal polyester resin contains at least 30 mol % of a repeating structural unit of the following formula A1 and has a flow temperature of 270xc2x0 C. to 400xc2x0 C., the inorganic filler in the form of fiber has an average fiber diameter of 0.1 to 10 xcexcm and a number-average fiber length of 1 to 100 xcexcm, the inorganic filler in the form of plate has an average particle size of 5 to 20 xcexcm, and the ratio (F/P) of the compounding amount (F) of the inorganic filler in the form of fiber to the compounding amount (P) of the inorganic filler in the form of plate satisfies the following equation;
0 less than F/P less than 0.5 or 1.6 less than F/P less than 10. 